1. Field of the Invention
The invention relates to the detection of specific nucleic acid sequences. More particularly, the invention relates to the detection of synthetic oligonucleotides present in body fluids or tissues.
2. Summary of the Related Art
Detection of specific nucleic acid sequences present in cells is generally known in the art. Southern, J,. Mol. Biol. 98:503-517 (1975) teaches detection of specific sequences among DNA fragments separated by gel electrophoresis, using "blotting" or transfer of the DNA fragments to a membrane, followed by hybridization of denatured DNA fragments with a radioactive probe and autoradiography. This procedure has also been extended to the detection of RNA molecules extracted from cells or tissues. More recently, faster and quantitative "dot-blotting" procedures have been developed for rapid detection of DNA or RNA from tissues or cells.
Recently, considerable interest has been generated in the development of synthetic oligonucleotides as therapeutic or gene expression modulating agents in the so-called antisense approach. For example, Agrawal, Trends in Biotechnology 10:152-158 (1991) extensively reviews the development of antisense therapeutic approaches. For an antisense therapeutic approach to be effective, oligonucleotides must be introduced into a patient and must reach the specific tissues to be treated. Consequently, there is a need to be able to detect oligonucleotides in body fluids or tissues. In animal models, radiolabelled oligonucleotides have been administered to the animal and their distribution within body fluids and tissues has been assessed by extraction of the oligonucleotides followed by autoradiography (See Agrawal, Temsamani and Tang, Proc. Natl. Acad. Sci. 88:7595-7599 (1991). As a practical matter, however, these methods cannot be extended to human patients. Unfortunately, the various techniques for detecting specific unlabelled nucleic acid sequences present in body fluids or tissues has only been extended to polynucleotides, such as large DNA or RNA molecules. Due to the small size of oligonucleotides, special problems relating to nonspecific binding or background, as well as to absence of binding, nondetection or false negatives exist. Thus, there remains a need to develop procedures for the detection of specific synthetic oligonucleotide sequences present in body fluids and tissues.